package com.hmdp.utils;

import cn.hutool.core.lang.UUID;
import org.springframework.core.io.ClassPathResource;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;

import java.util.Collections;
import java.util.concurrent.TimeUnit;

/**
 * 简单的redis分布式锁实现
 * 实现了自定义的ILock接口，提供获取锁和释放锁的功能
 */

public class SimpleRedisLock implements ILock {
    private String name;
    private StringRedisTemplate stringRedisTemplate;

    public SimpleRedisLock(String name, StringRedisTemplate stringRedisTemplate) {
        this.name = name;
        this.stringRedisTemplate = stringRedisTemplate;
    }


    private static final String KEY_PREFIX = "lock:";
    private static final String ID_PREFIX = UUID.randomUUID().toString(true)+'-';
    private static final DefaultRedisScript<Long> UNLOCK_SCRIPT;
    static {
        UNLOCK_SCRIPT=new DefaultRedisScript<>();
        UNLOCK_SCRIPT.setLocation(new ClassPathResource("unlock.lua"));  // resources 下路径
        UNLOCK_SCRIPT.setResultType(Long.class);
    }

    @Override
    public boolean tryLock(long timeoutSec) {
        //获取线程标识
        String threadId = ID_PREFIX+Thread.currentThread().getId();
        Boolean success = stringRedisTemplate.opsForValue().setIfAbsent(KEY_PREFIX + name, threadId + "", timeoutSec, TimeUnit.SECONDS);
        return Boolean.TRUE.equals(success);
    }


    @Override
    public void unlock() {
        // 改用 lua 脚本（保证原子性，将 判断锁 和 释放锁 放在一个脚本中，防止两个动作之间被阻塞）
        stringRedisTemplate.execute(
                UNLOCK_SCRIPT,
                Collections.singletonList(KEY_PREFIX+name),
                ID_PREFIX+Thread.currentThread().getId());
//        //获取线程标识，判断是不是这把锁，不能误删别的线程的锁
//        String threadId = ID_PREFIX + Thread.currentThread().getId();
//        String id = stringRedisTemplate.opsForValue().get(KEY_PREFIX + name);
//        // 线程id 是否与 锁中的id 一致
//        if(threadId.equals(id)) {
//            //释放锁
//            stringRedisTemplate.delete(KEY_PREFIX + name);
//        }
        //
    }
}


